In recent years with impending and localized shortages of fossil fuels, increased attention is directed toward solar energy as a source of energy to supply electricity, heating and for other purposes. It has been recognized for some time that the sun, at peak conditions, radiates to the earth approximately 1 kilowatt per square meter, which if collected with reasonable efficiency, would constitute a tremendous source of supplementary energy to mankind.
On a small scale, energy has been collected and converted to other forms of solar energy. The silicon solar cell is a prime example, but to date has been limited in efficiency and is high in unit cost. In France, a solar furnace has been developed capable of producing several thousand degrees in a small furnace. Numerous patents have been issued on various forms of solar energy conversion.
One of the biggest problems, given the capability of collecting solar energy, is the exchange of that energy into another usable form, for example, hot water or steam. Flat plate collectors usually achieve only lower temperature differences (.DELTA.T) and thus inefficient collection. Large arrays of point focus collector mirrors are capable of higher (.DELTA.T) and are capable of steam generation systems, for example. The battery of mirrors constituting the collectors must, however, be constantly trained to track the sun. The focal point is concentrated and must be moved relative to the collector on tracking or maintained stationary with the relatively large collector moving about. In any event, to have a small focus with a medium extremely high in temperature is of little value unless that temperature can be imparted to a continuous stream of heated medium such as water or steam. This is achieved more practically in elongated rather than circular collector configurations.
One extremely practical limitation is that in any system in which the furnace or parts thereof must be moved, it usually requires movable joints and seals for the heat exchange medium. Movable seals in steam, hot water or other fluid systems are the bane of the power generating engineer's existence. Great lengths have been taken in generation systems to minimize the number of seals percent.
One other major problem in focused solar energy collection systems is that the collectors required must necessarily provide mirrored surfaces many square meters in size and be movable and track the sun. Often the tracking control and actuation system exceeds the collector in complexity.
With the foregoing state of the art in mind, the following objects of this invention are sought:
(a) a low cost, efficient mirror system; PA1 (b) with a fixed receiver system; PA1 (c) with simple low cost tracking system; PA1 (d) with provision for simple tracking error correction; PA1 (e) with provision for easy replacement of mirror sections; PA1 (f) with provision for easy cleaning of mirror surfaces; PA1 (g) with thermal efficiency in both night time as well as during collection periods; PA1 (h) with provision for automatic maintenance of low moisture content receiver to maximize efficiency and reduce condensation; PA1 (i) with a large array with a single solar tracker which allows the entire array to be controlled by a single tracker.